1. Field of the Invention
The invention relates to a magnetic transducer, a thin film magnetic head using the same, a method of manufacturing a magnetic transducer and a method of manufacturing a thin film magnetic head. More particularly, the invention relates to a magnetic transducer having good thermal stability, a thin film magnetic head using the same, a method of manufacturing a magnetic transducer and a method of manufacturing a thin film magnetic head.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in a surface recording density of a hard disk or the like. A composite thin film magnetic head, which has a stacked structure comprising a reproducing head having a type of magnetic transducer, i.e., a magnetoresistive element (hereinafter referred to as an MR element) and a recording head having an inductive magnetic transducer, is widely used as the thin film magnetic head.
MR elements include an AMR element using a magnetic film (an AMR film) exhibiting an anisotropic magnetoresistive effect (an AMR effect), a GMR element using a magnetic film (a GMR film) exhibiting a giant magnetoresistive effect (a GMR effect), and so on.
The reproducing head using the AMR element is called an AMR head, and the reproducing head using the GMR element is called a GMR head. The AMR head is used as the reproducing head whose surface recording density exceeds 1 Gbit/inch2 (0.16 Gbit/cm2), and the GMR head is used as the reproducing head whose surface recording density exceeds 3 Gbit/inch2 (0.46 Gbit/cm2).
As the GMR film, a “multilayered type (antiferromagnetic type)” film, an “inductive ferromagnetic type” film, a “granular type” film, a “spin valve type” film and the like are proposed. Of these types of films, the spin valve type GMR film is considered to have a relatively simple structure, to exhibit a great change in resistance even under a low magnetic field and to be suitable for mass production.
FIG. 17 shows the structure of a general spin valve type GMR film (hereinafter referred to as a spin valve film). A surface indicated by reference symbol S in FIG. 17 corresponds to a surface facing a magnetic recording medium. The spin valve film has a stacked structure comprising an underlayer 91, a soft magnetic layer 92, a nonmagnetic layer 94, a ferromagnetic layer 95, an antiferromagnetic layer 96 and a capping layer 97, which are stacked in this order on the underlayer 91. In the spin valve film, the orientation of magnetization Mp of the ferromagnetic layer 95 is fixed by exchange coupling between the ferromagnetic layer 95 and the antiferromagnetic layer 96. The orientation of magnetization Mf of the soft magnetic layer 92 freely changes according to an external magnetic field. Resistance changes according to a relative angle between the orientation of the magnetization Mf of the soft magnetic layer 92 and the orientation of the magnetization Mp of the ferromagnetic layer 95.
For magnetic recording at ultra-high density exceeding 20 Gbit/inch2 (3.1 Gbit/cm2), it has been recently desired that the rate of change in electrical resistance of the spin valve film (hereinafter referred to as the rate of resistance change) should be made higher. For example, a cited reference “CoFe specular spin valves with a nano oxide layer”, 1999 Digests of INTERMAG 99, published on May 18, 1999 discloses that an oxide film called an NOL should be provided in the ferromagnetic layer of the spin valve film.
However, the above-mentioned cited reference gives no description about specific conditions such as a material and thickness of the oxide film called the NOL and a position into which the oxide film is to be inserted. Therefore, the applicant has proposed that the rate of resistance change should be increased by providing an interlayer made of, for example, an oxide film in an optimum position of the ferromagnetic layer or the soft magnetic layer of the spin valve film (see Japanese Patent Application No. Hei 11-227530).
However, the above-mentioned method may be unable to obtain a satisfactory result of thermal stability although the method can increase the rate of resistance change. The method has a problem, particularly in the case in which the interlayer is provided in the ferromagnetic layer.